Code Modernization: Introduce the spread operator in WP_HTTP_IXR_Client.

Rather than relying `func_get_args()` to retrieve arbitrary function arguments, we can now use the spread operator to assign them directly to a variable.

This makes the signature of `WP_HTTP_IXR_Client::query()` compatible with the parent class method.

Follow-up to [48204].

Props ayeshrajans.
See #48267, #47678.

git-svn-id: https://develop.svn.wordpress.org/trunk@48238 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/IXR/class-IXR-client.php

@@ -62,6 +62,8 @@ class IXR_Client
 	 * @since 1.5.0
 	 * @since 5.5.0 Formalized the existing `...$args` parameter by adding it
 	 *              to the function signature.
+	 *
+	 * @return bool
 	 */
     function query( ...$args )
     {

src/wp-includes/IXR/class-IXR-clientmulticall.php

@@ -44,6 +44,8 @@ class IXR_ClientMulticall extends IXR_Client
 	 * @since 1.5.0
 	 * @since 5.5.0 Formalized the existing `...$args` parameter by adding it
 	 *              to the function signature.
+	 *
+	 * @return bool
 	 */
     function query( ...$args )
     {

src/wp-includes/class-wp-http-ixr-client.php

@@ -46,10 +46,13 @@ class WP_HTTP_IXR_Client extends IXR_Client {
 	}
 
 	/**
+	 * @since 3.1.0
+	 * @since 5.5.0 Formalized the existing `...$args` parameter by adding it
+	 *              to the function signature.
+	 *
 	 * @return bool
 	 */
-	public function query() {
-		$args    = func_get_args();
+	public function query( ...$args ) {
 		$method  = array_shift( $args );
 		$request = new IXR_Request( $method, $args );
 		$xml     = $request->getXml();